In the past many different types of rotary steam engines have been built some by such eminent inventors as: Watt, Murdock, Hornblower, Trevithick, Ericsson, Maudslay and others but all the engines showed some disadvantages that in the end prevented their successful application. Most previously built large rotary steam engines showed extreme sealing problems and failed therefore mainly due to uncontrollable high steam leakages which gave cause to very low volumetric efficiencies. It is therefore one of the primary aims of the instant invention to demonstrate a contact-less gear-type labyrinth seal for this large rotary steam engine with very low steam leakage losses and with a therefrom resulting very high volumetric efficiency. Presently it is not economical to run conventional turbines or any rotary steam engines with steam temperatures much higher than 560.degree. C. due to erosion and corrosion effects such as cavitation or pitting of the rotor blades and other parts. Therefore it is a very important aim of the instant invention to show a large rotary steam engine capable of operating with steam temperatures higher than 560.degree. C. without the necessity of rotor blade cooling and the employment of expensive special steels. It is presently impossible to build large rotary steam engines capable of running with high steam pressures and high revolution due to incomplete internal pressure forces compensation. Therefore, it is an additional aim of the instant invention to show a rotary steam engine with a total internal radial and axial pressure forces compensation. Another important aim of the instant invention is to show a continuous smooth torque power output at the power take-off shaft as necessary for high power energy conversion application. Conventional steam turbines work at their maximum efficiency only at full load and a respective high rate of revolution. Under partial load condition the efficiency of conventional steam turbines deteriorates rapidly. It is therefore a further most important aim to show a rotary steam engine capable of operation at all load conditions with an efficiency equal or even higher than at full load condition. It is furthermore the aim of the instant inventions to show a rotary steam engine capable of operation with extreme wet steam, undegassed steam as well as steam containing large amounts of impurities.